1. Field of the Invention
The present invention relates generally to an epicyclic gear mechanism and, more particularly, an epicyclic gear mechanism constructed to switch over a power transmission path by changing over a rotating direction of a driving source such as a motor, etc.
2. Related Background Art
An already-known epicyclic gear mechanism rotationally driven by a driving source such as a motor is constructed to switch over a power transmission path to a plurality of driven mechanisms by changing over a rotating direction of the driving source like the motor. Considering a known zoom camera for example, when the motor rotates in one direction, its rotational driving force is transmitted to a zoom lens driving mechanism, thereby effecting a zooming action. When the motor rotates in the other direction, the power transmission path of the rotational driving force thereof is switched over. The rotational driving force is transmitted to a film winding/rewinding driving mechanism, whereby the film is fed. Further, as in the case of a camera motor drive device disclosed in Japanese Laid-Open Utility Model Application Sho/58-77327, a sun gear of the epicyclic gear mechanism is rotationally driven in one direction by the driving source such as the motor. A planet gear meshing therewith is made to revolve about the sun gear while rotating on its axis, thereby actuating a shutter release mechanism. Thereafter, the planet gear further revolves to mesh with a driving gear of a film winding mechanism. The sun gear is rotationally driven in the other direction by reversely rotating the motor. The film is thus rewound. The following defects, however, arise when employing the epicyclic gear mechanism in the manner described above and switching over the two power transmission paths in accordance with the rotating directions of the motor.
To be specific, the power transmission gear train to the driven mechanism receiving no transmission of the power is brought into a free state. Therefore, for instance, the film winding/rewinding driving mechanism makes irregular motions during zooming in the case of the zoom camera. The film deviates from a predetermined position. Besides, the zoom lens driving mechanism also makes irregular motions during the winding action of the film. A zoom lens barrel unexpectedly moves. Further, in the above-mentioned camera motor drive device, a film winding gear is not rotated during a release drive. The film winding gear is, however, engaged and therefore rotated by some external force during the release drive in some cases. This causes a frame displacement of the film and so on.
For eliminating this defect, the following construction is proposed as stated in, e.g., Japanese Laid-Open Patent Application Sho/55-98731. The planet gear is so supported on the lever as to be revolvable about the sun gear. The lever is provided with an engagement part for preventing the rotation of the other driven gear by engaging with the other driven gear when the planet gear meshes with one driven gear.
Based on the construction stated in Japanese Laid-Open Patent Application Sho/55-98731, however, the lever for stopping the other driven gear is pushed against the other driven gear by the revolving force of the planet gear. Therefore, when releasing the revolving force of the planet gear, i.e., the driving force of the motor, the stopping force of the other driven gear is relaxed. There exists a possibility where the other driven gear may rotate.